This invention relates to a technique for enabling a mobile terminal user to force a seamless handoff from a wireless telephony network to a wireless Local Area Network (LAN) interworked with the wireless telephony network.
Advances in the field of wireless LAN technology has led to the availability of relatively inexpensive wireless LAN equipment, which, in turn, has resulted in the emergence of publicly accessible wireless LANs (e.g., xe2x80x9chot spotsxe2x80x9d) at rest stops, cafes, libraries, and similar public facilities. Presently, wireless LANs offer users the opportunity to access private data networks, such as Corporate Intranets, and a public data networks such as the Internet. Few if any publicly accessible wireless LANs currently offers any type of telephone service, let alone, wireless telephony service.
Presently, users desirous of obtaining wireless telephony service typically subscribe to one of many providers of such service. Today""s wireless telephony service providers not only offer voice-calling capability, but also offer General Packet Radio Service (GPRS), thereby affording subscribers the capability of exchanging data packets via a mobile terminal. While GPRS exists in many areas, data transmission rates typically do not exceed 56 Kbs and the costs incurred by wireless network service providers to support this service remain high, making GPRS expensive.
The relatively low cost to implement and operate a wireless LAN, as well as the available high bandwidth (usually in excess of 10 Megabits/second) makes the wireless LAN an ideal access mechanism through which a mobile terminal user can exchange packets with a wireless telephony network. The advantages of higher bandwidth and lower access charges make the wireless LAN a more attractive access network than the wireless telephony network itself. Indeed, given a choice, most mobile terminal users would prefer to receive data communications service via a wireless LAN rather than directly from the wireless telephony network
Often, the coverage area available for a given wireless LAN will overlap the coverage area of a wireless telephony area with which the wireless LAN is interworked. Under such circumstances, the mobile terminal could receive access from either the wireless LAN or the wireless telephony network. Heretofore, effecting a seamless handoff of the mobile terminal user from the wireless telephony network to the wireless LAN has proven problematic. Presently, most wireless telephony networks effect handoff of a mobile terminal user from one cell to another in the network in accordance with the strength of signals exchanged with the mobile terminal user. The cell currently providing wireless telephony service constantly monitors the strength of signals exchanged with each mobile terminal user. Upon detecting a reduction in the received signal strength below a prescribed threshold, the cell initiates handoff of the mobile terminal user to an adjacent cell registering a higher received signal strength. As long as the current cell continues to register a received signal strength above the prescribed threshold, no handoff occurs. Thus, even if the mobile terminal user desires to receive service from a wireless LAN providing overlapping coverage, the user will continue to receive service from a cell in the wireless telephony network.
Thus, there is a need for a technique that enables a mobile terminal user to force a seamless handoff to a wireless LAN from a cell in the wireless telephony network.
Briefly, in accordance with present principles, a method is provided for effecting a seamless handoff of a mobile terminal user in a communications network from a first radio access mechanism to a second radio access mechanism. In a preferred embodiment, the first Radio access mechanism comprises a Radio Network Controller controlling an associated radio access node (e.g., a xe2x80x9ccellxe2x80x9d) in a wireless telephony network, while the second access mechanism comprises an Interworking Element that functions as a logical Radio Network Controller for controlling a radio access point in a wireless LAN. The method commences upon receipt of a request made by the mobile terminal user to receive service from the second radio access mechanism. Such a request triggers a command in the communications network to relocate (handoff) the mobile terminal, i.e., to redirect the data path away from the first radio access mechanism and through the second radio access mechanism. Responsive to the command, the second radio access mechanism is assigned to provide service to the mobile terminal user so that the user can commence a communications session and thereby exchange data packets with the network via the second radio access mechanism. Upon the assignment of the second radio access mechanism to the mobile terminal user, the first radio access mechanism is released so that the mobile terminal user no longer receives service therefrom.